Configuring wires/icons in a diagram. The diagram may be an executable diagram such as a graphical program or a system diagram. The diagram may include a plurality of icons that are connected by wires, and the icons may visually represent functionality of the diagram. The diagram may be executable to perform the functionality. Displaying the diagram may include displaying a first wire in the diagram, where the first wire connects a first icon and a second icon. Data transfer functionality may be specified for the first wire and/or the first or second icon in the diagram. The data transfer functionality may be visually indicated in the diagram, e.g., by appearances of the first icon, the second icon, the first wire, and/or icons displayed proximate to these components of the diagram.